Column-spring type snap-action electrical switch



Oct. 4, 1966 Filed Au 28, 1963 7", v 7. W W20 IHW SI ML INVENTOR. a p 30 35/ 37 BEM/AM/A/ Do a ra 2 BY g ATTORNEY United States Patent 3,277,257 COLUMN-SPRING TYPE SNAP-ACTION ELECTRICAL SWITCH Benjamin Doktor, 327 Thornton Road, Englewood, NJ. Filed Aug. 28, 1963, Ser. No. 305,153 7 Claims. (Cl. 200 ,67)

The present invention relates generally to improvements in electric switches and it relates more particularly to an improved snap switch.

Snap switches are usually of two types, tumbler switches and those employing column springs. The column spring type switch offers many advantages over the tumbler type. It is generally more comp-act and reliable and is considerably more sensitive than the tumbler type switch. However, the column type snap switches heretofore available possess many drawbacks. They are relatively expensive and often complex devices. Moreover, their actions are frequently conductive to fluttering, a condition which is highly undesirable and radically reduces the reliability and life of the switch and its overall usefulness. Thus, while the column spring snap switch is in wide commercial use, in many applications, it leaves much to be desired.

It is thus a principal object of the present invention to provide an improved electric switch.

Another object of the present invention is to provide an improved electric snap switch.

Still another object of the present invention is to provide an improved column spring snap switch.

A further object of the present invention is to provide an improved highly sensitive non-flutter snap switch.

Still a further object of the present invention is to provide an improved column spring snap switch of the above nature characterized by its simplicity, reliability, ruggedness, compactness and low cost.

The above and other obg'ects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a front perspective view of the column spring defining resilient strip employed in the subject switch and illustrated in its unstressed condition;

'FIGURE 2 is a front view of the resilient strip in its longitudinally compressed and constrained position and in its dormant equilibrium position;

FIGURE 3 is a view similar to FIGURE. 2 with the spring urged downwardly to its opposite equilibrium position;

FIGURE 4 is a vertical longitudinal sectional view of the improved switch; and

FIGURE 5 is ,a sectional view taken along line 5-5 in "FIGURE 4.

In a sense, the present invention contemplates the provision of an electric switch comprising a longitudinally constraint thereof.

According to a preferred form of the present device the resilient strip is in the form of a spring metal band bent at an obtuse angle approximately intermediate its ends to delineate upwardly diverging first and second sections. It should be noted that the stripnray be of desirable cross-section, for example, it may be formed of wire or rod to effect a highly compact structure. Moreover,

the strip sections may, in their unstressed conditions, be

"ice

linear or curved or of other suitable configuration which would permit of the longitudinal compression of the strip and a first section of lesser height than the second section. The strip is housed in a casing, the end walls of which engage the ends of the strip to effect the longitudinal compression and constraint thereof. A first contact element is carried by the first section between the ends thereof and a pair of second contacts are disposed on opposite sides of the first contact and are alternatively engaged thereby, the second contacts limiting the movement of the strip first section to upper and lower snap positions. An actuating element in the form of a sphere registers with a vertical bore formed in the casing and bears. on the convex face of the strip second section at a point offset from the crest thereof in a direction opposite to that of the first section. A hinged actuating arm bears on the upper face of the sphere. The contacts are connected to suitable terminals, the first contact preferably by way of a flexible conduct-or connected directly thereto.

Referring now to the drawings which illustrate a preferred embodiment of the present invention, the reference numeral 10 generally designates the improved switch which comprises a casing 11 formed in any suitable manner of an insulating material, preferably a synthetic organic resin such as nylon, polystyrene, polyester resin or the like. The casing 11 includes a heavy bottom wall 12, a horizontal top wall 13 and vertical end walls 14. Front and rear walls 16 and 1-7 respectively extend for the length of the casing 1 1 and project above the top wall 13 to provide longitudinally extending vertical flanges 18 and likewise project below the bottom wall 12. The casing 11 is provided with -a cavity 19 and a pair of longitudinally spaced transverse bores are formed in the bottom wall 12 and are engaged by metal bushings 20 which are upset at their ends and facilitate the mounting of the switch 10.

The switching mechanism includes a longitudinally extending resilient strip 21 defining a column spring and formed of spring steel or other suitable resilient material. While the column spring 21 is illustrated as being formed of a band, it may be formed of wire or other spring material of any desirable cross-section. The strip 21 is bent at preferably an obtuse angle at a point between the ends of the strip 21 to delineate first and second strip sections 22 and 23 respectively, the first section 22 preferably being somewhat longer than the second strip section 23. The spring strip sections 22 and 23 diverge upwardly from the elbow 24 formed by the bend in the strip 21 to form a dihedral. While the sections 22 and 23 in their unstressed state are illustrated as substantially straight, they may possess other configurations provided that they meet at the parameters hereinafter set forth, for example, the second strip section 23 may be curved with its top face upwardly convex and the first strip section 22 may be likewise curved, but preferably only to a minor degree.

Formed in the bottom confronting faces of the end walls 14 at the level of the bottom wall 12 are transversely extending seat defining corners 26, the distance between the corners 26 being less than the distance between the free ends of the spring strip 21 in its unstressedcondition. The strip 21 is longitudinally compressed and housed in the cavity 19, the free ends of the strip 21 engaging the corners 26 to constrain the strip 21 in its longitudinally compressed condition. In the above compressed and con strained condition, the strip 21 bows upwardly, as a whole, in the cavity 19 both sections 22 and 23 thereof tending to individually bow upwardly between their free end and the elbow-defining bend 24. A button contact element 27 formed of a suitable metal is mounted on the strip first section 22 between the ends thereof and is provided with top and bottom convex curved contact surfaces 28 and 29 respectively, disposed above and below the strip section 22.

A first terminal post defined by a vertical leg 30 is affixed in and registers with and extends below a corresponding opening formed in the base wall 12 adjacent to the free end of the first strip section 22. The post 30 terminates at its top below the upper face of the casing bottom wall 12. A highly flexible conductor strip or wire 36 electrically connects the contact button 27 to the post 30, passing from the contact element 27 along the top face of the strip section 22 and around the free end thereof and through a corresponding slot formed in the casing walls and is secured to the post 30. This expedient inhibits any resistance heating of the column spring strip 21 and any change in the physical characteristics thereof. A second terminal post 37 includes a vertical leg 38 registering with and depending below a corresponding bore formed in the bottom wall 12 at a point between the button contact 27 and the strip bend 24. The post 38 terminates -at its top in a laterally extending horizontal leg 39 which is directed toward the post 36 and nests in a corresponding well 40 formed in the top face of the casing wall 12. Aflixed to the leg 39 adjacent to its free end is a contact element or button 41 having a top face confronting and in vertical registry with the button contact surface 29 of the contact button 27.

A third terminal post 42 includes a vertical leg 43 registering with and projecting above and below a corresponding bore formed in the bottom wall 12 adjacent to the rear wall 17 and disposed in the vicinity of the contact button 27. The vertical leg 43 terminates at its upper end in an inwardly directed transverse horizontal leg 44 located between the con-tact button 27 and the casing upper wall 13. A tapped bore is formed in the horizontal leg 44 in vertical registry with the contact button 27 and is engaged by a contact element defining screw 46 provided with a slotted head 47 which rotatably and slidably registers with the corresponding opening formed in the casing top wall 13. It should be noted that the contact elements 41 and 46 define, in addition, upper and lower detents or stop members to limit respectively the upper and lower movement of the first spring section 22. The upper limit of movement of the first spring section 22 is adjustable by means of the screw 46.

In order to facilitate the control of the switching mechanism between its upper and lower limits as delineated by the contact elements 41 and 46, a vertical circular bore 47 is formed in the casing top wall 13 and a steel ball or sphere 48 vertically slidably registers with the bore 47 and rests on the upper convex face of the spring strip second section 23, advantageously at a point slightly oifset from the crest thereof in a direction opposite to that of the first spring strip section 22. A channel-shaped lever 49 is pivoted adjacent one end thereof for swinging about a transverse axis by means of a pin 50 between the upper flanges 18 adjacent an end wall 14 in the vicinity of the spring section 23. A bearing button 51 is affixed to the underface of the lever 49 and bears upon the upper surface of the sphere 48. Formed in the base of the channelshaped lever 49 is an opening 52 which affords access to the contact screw head 47.

Considering now the operation of the switch described above, in its normal dormant position the column spring 21 is longitudinally compressed and constrained by the seats 26 in end walls of the casing 11 so that the spring strip 21 is bowed upwardly, the sections 22 and 23 assuming bows of different heights. The bowing of the first section 22 is limited by the contact stop element 46 to a height considerably less than that of the second spring section 23. In the aforesaid position the contact element 27 is in engagement with the contact screw 46 to complete the circuit between the terminal posts 32 and 33. Upon depression of the lever 49, the sphere 48 is urged downwardly to correspondingly depress the bowed second spring section 23. Until the section 23 has been depressed to a critical point, the contact button 27 is spring maintained in firm engagement with the contact element 46. However, upon the sphere 48 depressing the spring second section 23 to a point below a dead center or critical equilibrium point, the first spring section 22 snaps from its upper normal snap position to its lower pressure snap position into firm spring-urged engagement with the lower contact element 41 to open the circuit between the terminal posts 30 and 42 and close the circuit between the posts 37 and 42. Upon release of the lever 49 the spring strip 41 immediately snaps to its initial position as illustrated in FIGURE 4 of the drawing. It should be noted that attendant to the switching operation the surfaces 28 and 29 of the contact button 27 wipe along the corresponding contact elements 46 and 41 under pressure before movement between the normal snap and pressure snap positions is effected to thereby assure the continued cleanliness of the contact surfaces.

While there has been described and illustrated a preferred embodiment of the present invention, it is apparent that numerous alterations, omissions and additions may be made without departing from the spirit thereof.

What is claimed is:

1. An electric snap switch comprising a housing including fixed end walls, a spring strip having a preset bend between its ends delineating adjacent first and second sections separated by said bend and diverging therefrom at an obtuse angle, said spring strip being disposed in said housing and longitudinally compressed and constrained by said fixed end walls to normally bow said first and second sections in a common direction, a pair of first and second stop members disposed on opposite sides of said first section and limiting the bowing thereof to a lesser height than the bowing of said second section and the movement thereof to opposite normal snap and pressure snap positions, and a movable actuating element engaging the normally convex face of said second section at a point remote from the end thereof and located at the apex of said second section or at either side of said apex whereby to permit the application of pressure to said second section convex face to urge said first section toward said pressure snap position.

2. The switch of claim 1, wherein at least one of said stop: members is electrically conducting and defines a pole of said switch and including a contact element carried by said first section which alternatively engages said stop members.

3. The switch of claim 1 wherein said actuating element engages said second section top face at a point offset from the crest thereof in a direction opposite to said first section.

4. The electric switch of claim 1, wherein said housing includes a wall having a bore formed therein, said actuating element slidably registering with said bore.

5. The electric switch of claim 4, wherein said actuating element is defined by a sphere bearing upon said second section top face.

6. The electric snap switch of claim 1 wherein said movable actuating element includes a ball member bearing on said normally convex face of said second section.

7. An electric snap switch comprising a base provided wit-h a pair of longitudinally spaced abutment faces, a spring strip having a preset bend between its ends delineating adjacent first and second sections separated by said bend and diverging therefrom at an obtuse angle, said spring strip being disposed between said abutment faces and compressed and constrained by said abutment faces to normally bow said first and second sections in a common direction said second section havinga greater degree of curvature than said first section, a stop member engaging a convex face of one of said bowed spring sections to limit the bowing thereof in said common direction, and a movable actuating element engaging the normally convex face of said second section at a point remote from the end thereof and at the apex thereof or at either side of the apex of said second section whereby to permit the application of pressure to said second section convex face to urge said first section in a direction opposite said common direction toward a pressure snap position.

References Cited by the Examiner UNITED STATES PATENTS 6 FOREIGN PATENTS 956,154 7/1949 France.

5 ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

H. B. ODONNELL, D. SMITH, ]R.,

Assistant Examiners. 

1. AN ELECTRIC SNAP SWITCH COMPRISING A HOUSING INCLUDING FIXED END WALLS, A SPRING STRIP HAVING A PRESET BEND BETWEEN ITS ENDS DELINEATING ADJACENT FIRST AND SECOND SECTIONS SEPARATED BY SAID BEND AND DIVERGING THEREFROM AT AN OBTUSE ANGLE, SAID SPRING STRIP BEING DISPOSED IN SAID HOUSING AND LONGITUDINALLY COMPRESSED AND CONSTRAINED BY SAID FIXED END WALLS TO NORMALLY BOW SAID FIRST AND SECOND SECTIONS IN A COMMON DIRECTION, A PAIR OF FIRST AND SECOND STOP MEMBERS DISPOSED ON OPPOSITE SIDES OF SAID FIRST DIRECTION AND LIMITING THE BOWING THEREOF TO A LESSER HEIGHT THAN THE BOWING OF SAID SECOND SECTION AND THE MOVEMENT THEREOF TO OPPOSITE NORMAL SNAP AND PRESSURE SNAP POSITIONS, AND A MOVABLE ACTUATING ELEMENT ENGAGING THE NORMALLY CONVEX FACE OF SAID SECOND SECTION AT A POINT REMOTE FROM THE END THEREOF AND LOCATED AT THE APEX OF SAID SECOND SECTION OR AT EITHER SIDE OF SAID APEX WHEREBY TO PERMIT THE APPLICATION OF PRESSURE TO SAID SECOND SECTION CONVEX FACE TO URGE SAID FIRST SECTION TOWARD SAID PRESSURE SNAP POSITION. 